Apply classic sudoku rules. The grey central box serves as an exemplar. The four corner boxes are compared to the central one and the result of comparison is given in the style of a Mastermind puzzle for every triplet of cells. A black dot is given for every identical digit in the same position. A white dot is given for an identical digit but not in the same position. A cross means that there is nothing in common in this triplet.
Notes:Variants:
- Place a digit from 1 to 9 into each of the empty cells so that each digit appears exactly once in each row, column and 3x3 outlined box. The black and white dots to the right of the grid compare the five marked cells in that row to the mastermind code. Black dots imply correct digits in the correct position while white dots imply correct digits in the wrong position. There must not be any repeating digits in the code.